Effects of position on oesophageal function: studies using combined manometry and multichannel intraluminal impedance.

Multichannel intraluminal impedance (MII) allows assessment of intraoesophageal bolus transit. In the supine position, bolus transit is produced almost exclusively by peristaltic contractions; in the upright position, gravity also contributes to bolus transit. MII and peristaltic pressures were measured in four positions (0, 30, 60 and 90 degrees ) using ten swallows (5 cc each) of both water and viscous liquid with body position determined by random choice. Tracings were analysed for total bolus transit time: time interval between bolus entry at 20 cm above and bolus exit at 5 cm above the lower oesophageal sphincter (LOS) and contraction amplitudes at 5 and 10 cm above the LOS. Statistical comparison of mean values of all four body positions was done using anova and Bonnferoni post-test. Ten normal subjects (five females and five males, age 24-45 years) completed the study. At each body position, liquid material transited faster (P < 0.001) than viscous material. Both liquid and viscous materials transited at lower inclinations (0 and 30 degrees ) significantly slower than at higher inclinations (60 and 90 degrees ). There was an almost perfect inverse linear correlation between angle of inclination and bolus transit time for both liquid (r = -0.99) and viscous (r = -1.00) boluses (Spearman correlation r > 0.99 and P < 0.02 for both substances). Contraction amplitudes for liquid vs viscous material were not significantly different at a given degree of inclination. Mean distal oesophageal amplitude declined with increasing inclination. Combined MII-OM identifies and quantifies the effects of gravity on the dichotomy between specific pressures measured by OM and function assessed as transit measured by MII.